Editing Operation Sea Lion (section)

=== Outbreak of war and fall of Poland ===
In September 1939, the successful<ref>
* [[Richard Overy|Overy, R. J.]] (1998) ''The Origins of the Second World War'' London: Longmans. p. 84 {{isbn|0-582-29085-6}}
* [[John Keegan|Keegan, John]] (1986) ''The Second World War'' New York: Morrow. p. 76
* [[Alan Bullock|Bullock, Alan]] ''Hitler and Stalin'' New York: Knopf. p. 644. {{isbn|0-394-58601-8}}
* [[Richard J. Evans|Evans, Richard J.]] (2008) ''[[The Third Reich at War]]'' New York: Penguin. p. 6 {{isbn|978-0-14-311671-4}}</ref> German [[invasion of Poland]] infringed on both [[Franco-Polish alliance (1921)|a French]] and [[Anglo-Polish military alliance|a British]] alliance with Poland and both countries declared war on Germany. On 9 October, Hitler's "Directive No. 6 for the Conduct of the War" planned an offensive to defeat these allies and "win as much territory as possible in Holland, Belgium, and northern France to serve as a base for the successful prosecution of the air and sea war against England".<ref name="Directive 6">{{harvnb | Murray | 2002 | pp=[http://www.ibiblio.org/hyperwar/AAF/AAF-Luftwaffe/AAF-Luftwaffe-2.html#fn28 32–33, 35]}}, [http://der-fuehrer.org/reden/english/wardirectives/06.html Directive No. 6 for the Conduct of the War] {{webarchive|url=https://web.archive.org/web/20160729073651/http://der-fuehrer.org/reden/english/wardirectives/06.html |date=29 July 2016 }}, Berlin, 9 October 1939</ref>

With the prospect of the Channel ports falling under ''[[Kriegsmarine]]'' (German Navy) control, Grand Admiral (''[[Großadmiral]]'') [[Erich Raeder]] (head of the ''Kriegsmarine'') attempted to anticipate the obvious next step that might entail and instructed his operations officer, ''[[Kapitän zur See|Kapitän]]'' [[Hansjürgen Reinicke]], to draw up a document examining "the possibility of troop landings in England should the future progress of the war make the problem arise". Reinicke spent five days on this study and set forth the following prerequisites:
* Eliminating or sealing off [[Royal Navy]] forces from the landing and approach areas.
* Eliminating the [[Royal Air Force]].
* Destroying all Royal Navy units in the coastal zone.
* Preventing [[Royal Navy Submarine Service|British submarine]] action against the landing fleet.<ref name=Ansel43>Ansel, p. 43</ref>
On 22 November 1939, the Head of ''[[Luftwaffe]]'' (German Air Force) intelligence [[Joseph Schmid|Joseph "Beppo" Schmid]] presented his "Proposal for the Conduct of Air Warfare", which argued for a [[Blockade of Germany (1939–45)|counter to the British blockade]] and said "Key is to paralyse the British trade" by blocking imports to Britain and attacking seaports. The OKW (''[[Oberkommando der Wehrmacht]]'' or "High Command of the Armed Forces") considered the options and Hitler's 29 November "Directive No. 9 – Instructions For Warfare Against The Economy of the Enemy" stated that once the coast had been secured, the ''Luftwaffe'' and ''Kriegsmarine'' were to [[blockade]] UK ports with sea mines, attack shipping and warships, and make air attacks on shore installations and industrial production. This directive remained in force in the first phase of the Battle of Britain.<ref name="Directive 9">{{harvnb| Overy | 2013 | p=68}}, [http://der-fuehrer.org/reden/english/wardirectives/09.html Directive No. 9 – Instructions For Warfare Against The Economy of the Enemy] {{webarchive|url=https://web.archive.org/web/20160304050359/http://der-fuehrer.org/reden/english/wardirectives/09.html |date=4 March 2016 }}, Berlin, 29 November 1939.</ref>

[[File:The British Army in France 1939 O86.jpg|thumb|British soldiers in France in 1939]]
In December 1939, the [[German Army (Wehrmacht)|German Army]] issued its own study paper (designated ''Nordwest'') and solicited opinions and input from both the ''Kriegsmarine'' and the ''Luftwaffe''. The paper outlined an assault on England's eastern coast between [[The Wash]] and the [[River Thames]] by troops crossing the [[North Sea]] from ports in the [[Low Countries]]. It suggested airborne troops as well as seaborne landings of 100,000 infantry in [[East Anglia]], transported by the ''Kriegsmarine'', which was also to prevent Royal Navy ships from getting through the Channel, while the ''Luftwaffe'' had to control airspace over the landings. The ''Kriegsmarine'' response was focused on pointing out the many difficulties to be surmounted if invading England was to be a viable option. It could not envisage taking on the Royal Navy [[Home Fleet]] and said it would take a year to organise shipping for the troops. ''[[Reichsmarschall]]'' [[Hermann Göring]], head of the ''Luftwaffe'', responded with a single-page letter in which he stated, "[A] combined operation having the objective of landing in England must be rejected. It could only be the final act of an already victorious war against Britain as otherwise the preconditions for success of a combined operation would not be met".<ref name=Ansel47-49>Ansel, pp. 47–49</ref>{{sfn|Bishop|2009|pp=106–07}}